The city of Longueuil, Que., is in crisis, after a diesel fuel spill raised concerns the water supply is unfit to drink.

Around 300,000 people in the city, and surrounding area, have been asked not to drink the tap water, after an estimated 28,000 litres of fuel spilled, spread through the sewer system and ended up in the Saint-Lawrence River early Wednesday morning.

The leak happened at 4 a.m. after a pipe carrying diesel to an emergency generator at the city's water treatment plant sprung a leak.

An official from Monteregie public health does not recommend drinking the water, but he says doing so won’t result in serious health effects.

"We advise not to drink the water, but if they do we don’t think there will be serious health effects because it was diluted," Dr. Marc Lemieux told CTV Montreal.

He added that it was unlikely people would drink the water because of its odour.

Officials say there is little chance the diesel made its way into the city's treated water supply, but did find traces of the fuel on the surface of an untreated water tank.

"Some of that diesel that stayed underground might have contaminated a part of the drinkable water system," said Jacques Tetreault, a representative for the City Longueil.

As a precaution, residents have also been warned not to boil water, and to drink bottled water instead.

Because they did not learn of the spill until 9:30 a.m. on Wednesday, more than five hours after it occurred, Quebec's environment ministry says they were notified too late to attempt a clean-up before the contamination spread.

The City of Longueil initially said that local tap water was unaffected by the spill.

"At the time we had no information that this leak could lead to a problem with drinking water, so everything was fine for a few hours, but early this morning some citizens complained about a gas smell," said Tetreault.

The city's mayor, Caroline St-Hilaire, said a water advisory was issued as quickly as possible to ensure they were on the same page as the Quebec's health and environment ministers.

Tetreault added that workers needed time to figure out the source of the leak.

David Heurtel, the province's environment minister, promised an investigation to figure out what happened.

"Once we have an understanding of all the facts then if there are to be consequences, legal or otherwise. Obviously the ministry will act accordingly," he said.

Longueuil has opened distribution centres where residents can pick up drinking water. Some residents had to wait three hours for the water to arrive at one centre, at Colisee Jean Beliveau on Jacques Cartier Blvd. E.

The water advisory remains in effect until further notice.

The following is a list of the distribution centres:

Vieux-Longueuil

  • 1100 Marie-Victorin St.
  • Chalet Saint-Charles, 195 Chateauguay St.
  • Colisee Jean Beliveau, 1755 Jacques Cartier St. E
  • Arena Olympia, 2950 Dumont St.
  • Fire station 31 in the Le Moyne sector, 2205 Saint-Georges St.

Saint-Hubert

  • Garage de la Direction des travaux publics, 6355 Maricourt Blvd.
  • Centre sportif Rosanne Laflamme, 7405 du Centre Terrace

Greenfield Park

  • Fire station 33 in Greenfield Park, 1510 Bellevue St.
  • Garage de la Direction des travaux publics, 4130 Grande Allee — coming soon

Boucherville

  • Centre sportif Pierre-Laporte, 490 chemin du Lac
  • Centre multifonctionnel, 1075 Lionel Daunais St.
  • Église Saint-Sébastien, 780 Pierre-Viger St.
  • Centre communautaire Saint-Louis, 220 Claude Dauzat St.

Brossard

  • Fire station 43 in Brossard, 3300 Lapiniere Blvd.
  • Saint-Bruno — coming soon
  • Centre Marcel-Dulude, 530 Clairevue Blvd. W

Saint-Lambert

  • Fire station 41, 55 Argyle St.

With files from Kieron Lang and CTV Montreal's Maya Johnson and Cindy Sherwin